Search Results (2,917)

Electrocatalytic glycerol oxidation to formic acid (FA) offers a sustainable route for biomass valorization, yet non-noble metal catalysts generally suffer from sluggish C-C bond cleavage and poor product selectivity. Here we report an amorphous nickel–cobalt oxyhydroxide bearing both metal and oxygen vacancies (D-NiCoO_xH_y-V_Cr,O), grown on nickel foam via one-step electrodeposition followed by electrochemical activation with Cr doping. The coexistence of the dual vacancies is experimentally confirmed by X-ray photoelectron spectroscopy (XPS), which reveals elevated Ni³⁺/Co³⁺ ratios and reduced lattice oxygen, and by electron paramagnetic resonance (EPR), which shows a markedly enhanced signal at g = 2.003. Building on prior Cr-leaching approaches in single-metal nickel oxides, this work extends dual-vacancy engineering to an amorphous bimetallic NiCo oxyhydroxide and correlates the defect structure with glycerol-induced interfacial responses, charge-transfer behavior, and product selectivity. The catalyst delivers 200 mA cm⁻² at 1.31 V vs. RHE and achieves 100% Faradaic efficiency for formate at 1.32 V vs. RHE. In situ electrochemical impedance spectroscopy further reveals a significantly reduced charge-transfer resistance. These results establish Cr-assisted dual-vacancy engineering in amorphous bimetallic oxyhydroxides as a promising strategy for selective biomass electrooxidation. Full article

Nickel release from metallic items is the leading cause of allergic contact dermatitis, and preventive strategies require both reliable detection tools and materials capable of limiting skin exposure. In this work, we propose dual-function bioplastic coatings based on starch, glycerol, and cellulose derivatives incorporating dimethylglyoxime (DMG) and a pH-10 borate buffer to enable colorimetric nickel sensing directly in the solid state. The Ni–DMG assay was first optimized in solution through UV-Vis spectroscopy and a Central Composite Face-Centered Design, identifying reagent concentrations that maximize linearity while minimizing detection limits. These conditions were transferred to bioplastic films prepared using carboxymethyl cellulose (CMC) or quaternized hydroxyethyl cellulose ethoxylate (QHECE). The materials were characterized by FT-IR spectroscopy and Principal Component Analysis, while gravimetric tests assessed hydrophilicity. Both bioplastics showed clear and reproducible colorimetric responses upon nickel exposure, and multivariate models built from RGB values and UV-Vis spectra enabled quantitative prediction of Ni²⁺ content. However, the proof-of-concept experiment revealed insufficient resistance to prolonged moisture, with films softening and partially losing cohesion under conditions mimicking skin perspiration. These results demonstrate that the sensing mechanism is robust, but the current bioplastic formulation requires improved water resistance before practical deployment as protective coatings for jewelry. Full article

The imperative to mitigate climate change has accelerated the development of Carbon Capture, Utilization, and Storage (CCUS) technologies, particularly CO₂ hydrogenation into high-value chemicals and alternative fuels. This work evaluates the fundamental thermodynamic limitations and the primary directions of CO₂ conversion, with a primary focus on methanation, alongside related pathways such as methanol synthesis and the reverse water-gas shift (RWGS) reaction. To overcome the high kinetic barriers of CO₂ activation, various catalytic systems are analyzed. While noble metal catalysts exhibit high catalytic performance, nickel-based catalysts serve as a viable and cost-effective alternative. To overcome nickel’s susceptibility to thermal sintering and coking, advanced bimetallic and multimetallic formulations are being developed to enhance structural stability and selectivity. These advancements are crucial for producing Synthetic Natural Gas (SNG) and sustainable aviation fuels (SAF). Ultimately, the objective of this comprehensive review is to systematically summarize recent advancements in catalyst design, critically analyze the advantages and fundamental bottlenecks of distinct catalytic systems, and outline prospective paths for the efficient industrial-scale production of sustainable alternative fuels. Full article

Metal foams and nanofluids are recognized as attractive and effective heat transfer enhancement methods. This study numerically investigates forced convection heat transfer and second-law thermodynamic behavior of water and a 0.02% Cu–MXene/water hybrid nanofluid flowing through a tube partially filled with metal foam. Three configurations are examined: a clear tube as the reference case; Case A (three discrete foam blocks occupying 3/16 of the tube length); and Case B (a single block occupying 9/16), using four metal-foam types (aluminum 30/45 PPI, copper 40 PPI, and nickel 60 PPI). The governing equations are solved using the finite-volume method with the SIMPLER algorithm and validated against published experimental and numerical data. Results show that Case B provides higher heat-transfer rates and performance evaluation criterion (PEC) values than Case A, although at the expense of larger pressure-drop and pumping-power penalties. The highest heat-transfer enhancement is obtained with Cu-40 PPI foam and the hybrid nanofluid in Case B, where the average Nusselt number increases by a factor of 3.33 at a Reynolds number of Re = 200 relative to water in the clear tube. Higher-thermal-conductivity foams, combined with the hybrid nanofluid, provide greater thermohydraulic benefits than lower-conductivity foams with water. The second-law analysis reveals that increasing Re reduces thermal irreversibility but increases frictional irreversibility, highlighting the competing effects of heat-transfer enhancement and hydraulic resistance. Overall, the Cu-40 PPI/hybrid nanofluid combination in Case B at low Re provides the most favorable performance among the investigated conditions. Full article

MOF-derived catalysts have considerable potential for aqueous contaminant control, but their practical application is often constrained by the aggregation and difficult recovery of powder catalysts. In this study, a self-supporting N-doped Fe/Ni-based monolithic catalyst, denoted N-101-NFF, was fabricated through the in situ growth of an Fe-based MOF precursor on nickel–iron foam followed by pyrolysis. Under the conditions of 50 mg/L chlortetracycline (CTC), 0.08 mmol/L peroxymonosulfate (PMS), and an effective catalyst area of 1 cm², N-101-NFF degraded 90.3% of CTC within 60 min and maintained a degradation efficiency of 88.6% after five consecutive cycles. Quenching experiments and EPR analysis indicated the involvement of •OH, SO₄•⁻, O₂•⁻, and ¹O₂ in CTC degradation. Electrochemical measurements indicated improved interfacial charge-transfer characteristics, while post-reaction XPS analysis revealed changes in the Fe and Ni valence states and surface N- and O-containing groups, supporting the involvement of Fe and Ni redox cycling and these surface functionalities in PMS activation. In a fixed-bed reactor, the system maintained more than 86% CTC removal over 24 h of continuous-flow operation at a CTC feed rate of 200 mL/h. These results highlight the potential of N-101-NFF as a recoverable monolithic catalyst for PMS-based treatment of antibiotic-contaminated water. Full article

This study explores the multifunctional properties of Ni nanoparticles obtained by laser ablation in liquid, with emphasis on the potential use of these nanoparticles in different applications such as cooling fluids or photoelectrochemical ones. The Ni nanoparticles were synthesized by the laser ablation in liquid technique using an Nd-YAG laser and ultrapure water as liquid. The structural, dimensional, morphologic, and stoichiometric characterizations of the nanoparticles were performed using different techniques such as transmission electron microscopy (TEM), energy dispersive X-ray (EDS) and dynamic light scattering spectroscopy (DLS). Nickel nanoparticles with sizes ranging from 5 to 15 nm in diameter were obtained. The experimental measurements were performed to determine the thermal conductivity and viscosity of the obtained nanofluids, essential parameters in the evaluation of the cooling fluid performances. Loading TiO₂ thin films with Ni nanoparticles led to the enhancement of the photoelectrochemical water splitting properties of TiO₂ thin films, the Ni nanoparticles acting on the collecting, transferring and separating the photogenerated charges and ultimately improving the overall anodic and cathodic efficiencies. The results obtained can contribute to the development of innovative, multifunctional solutions based on non-precious metals for cooling and water splitting systems used in industrial, electronics and other applications. Full article

This study provides baseline information for environmental assessment in North Riyadh, Saudi Arabia. It assessed the concentrations of eight heavy metals, namely cobalt (Co), chromium (Cr), copper (Cu), iron (Fe), nickel (Ni), lead (Pb), vanadium (V), and zinc (Zn), in 28 surface soil samples collected across the area. Pollution status was evaluated using the contamination factor (CF), geoaccumulation index (Igeo), enrichment factor (EF), pollution load index (PLI), and degree of contamination (DC), while Pearson correlation, principal component analysis (PCA), and standardized hierarchical cluster analysis (HCA) were applied to identify the possible sources of these metals. Iron was the most abundant element (mean 8482.14 mg kg⁻¹), consistent with its role as a major crustal constituent. Co, Cr, Fe, Ni, and V showed low contamination (CF < 1) and a predominantly geogenic origin, reflected in strong inter-element correlations and a dominant rotated principal component explaining 54.8% of the total variance; Cu, Pb, and, in particular, Zn departed from this pattern, loading together on a distinct secondary component (32.1% of variance) and showing localized enrichment at a small number of sites. None of the 28 samples exceeded the pollution threshold for PLI (all < 1) or DC (all < 8), indicating that the soils of North Riyadh remain overall unpolluted with respect to these eight metals. These findings provide an early geochemical baseline for the district and identify Cu–Pb–Zn enrichment near construction and traffic corridors. Full article

CO₂ methanation is a promising power-to-gas technology that enables the conversion of carbon dioxide into methane. However, the development of efficient catalysts based on naturally abundant and inexpensive support remains an important challenge. In this work, metakaolin from natural kaolin was investigated as a novel support for high-loading (30 wt.%) Ni catalysts prepared using a melt infiltration method. The influence of CeO₂ and alkaline earth metal oxides (MgO, CaO) on the physicochemical properties and catalytic performance was systematically evaluated. It was evidenced that CeO₂ improved NiO reducibility, whereas MgO and CaO promoted Ni⁰ dispersion and modified textural and surface properties. In particular, Mg addition increased the S_BET from 23 to 39 m²/g and the total pore volume from 0.06 to 0.17 cm³/g compared with the Ni-MK sample. The promoted catalysts exhibited enhanced low-temperature activity and reached approximately 80% CO₂ conversion at 400 °C, close to thermodynamic equilibrium, maintaining CH₄ selectivity above 97%. Stable catalytic performance was preserved during 24 h time-on-stream tests. The results demonstrate that metakaolin is a promising sustainable support for Ni CO₂ methanation catalysts and that melt infiltration provides a simple and effective preparation route for obtaining high nickel loading. Full article

This systematic review aimed to evaluate whether cross-sectional geometry is associated with cyclic fatigue resistance of nickel–titanium (NiTi) endodontic instruments and to identify the geometric and materials-related features most frequently associated with improved fatigue performance. The protocol was prospectively registered on the Open Science Framework (OSF). PubMed, Scopus, Embase, Web of Science, and WorldCat were searched in April 2026 in accordance with PRISMA 2020. Eligible studies were comparative in vitro investigations that explicitly evaluated cross-sectional geometry or a related geometric parameter as a prespecified study factor and reported quantitative cyclic fatigue outcomes. Of 107 screened records, 66 full-text reports were assessed and 23 studies were included in the qualitative synthesis. Twenty-two studies had a medium risk of bias and one had a low risk of bias according to the Quality Assessment Tool for In Vitro Studies (QUIN). Cyclic fatigue resistance was most often reported as time to fracture or number of cycles to failure. Instruments with reduced metal mass, smaller core volume, lower cross-sectional area, and greater flexibility tended to demonstrate higher fatigue resistance in curved canals. S-shaped and double-S-shaped cross-sections were most consistently associated with favorable outcomes; however, this association is more plausibly related to reduced bending stiffness and canal-wall contact forces than to increased intrinsic material fatigue strength. Flat-side designs did not show a consistent advantage. The evidence was limited by heterogeneous testing protocols and residual confounding by alloy, heat treatment, taper, manufacturing, surface condition, and kinematics. No meta-analysis or quantitative dimensional correlation was feasible because testing conditions and detailed geometric parameters were inconsistently reported. Full article

The crystal structure and physicochemical properties of a new Ni/Zn codoped bismuth antimonite pyrochlore, synthesized by the solid-phase reaction method, were investigated. The most optimal outcomes of Rietveld refinement for Bi_2.7Zn_0.46Ni_0.70Sb₂O_10+Δ were achieved for the model of a disordered pyrochlore structure (sp.gr.Fd-3m:2, a = 10.46442(5) Å). Zinc and nickel atoms demonstrate an inhomogeneous mixed distribution across bismuth and antimony positions. The microstructure of the ceramic is characterized by low porosity, and is formed by faceted grains of 0.25–2 μm in diameter. The thermal expansion coefficient (TEC) increases monotonically from 7.14 × 10⁻⁶ °C⁻¹ (30 °C) to 9.80 × 10⁻⁶ °C⁻¹ (990 °C). At temperatures above 1080 °C, an atypical thermal dissociation of the pyrochlore occurs, resulting in the formation of bismuth-free compounds and two cubic phases that are stable when the sample is cooled. The Bi_2.7Zn_0.46Ni_0.70Sb₂O_10+Δ compound is characterized by a band gap width of 2.4 eV. At temperatures below 200 °C, the sample exhibits predominantly capacitive impedance characteristics. The capacitance remains constant and independent of temperature and frequency up to a maximum of 150 °C. The high-frequency relative dielectric permittivity is low and equal to 26(3). The conduction activation energy in the sample is found to be 1.30(5) eV. Two polarization processes are detected in the sample. The electrical behavior of the sample has been modeled successfully by equivalent circuits within the temperature range of 200–450 °C. According to NEXAFS and XPS data, metal cations exhibit a conventional charge state, with an antimony oxidation state of +(5−δ). Full article

This study evaluates the effects of novel metal-based fuel additives on the combustion, thermal behavior, and emissions of a common-rail diesel engine. Two transition metal complexes, Bis-[N-(1,1′-biphenyl)-2-chlorobenzoylthioureato]nickel(II) (NiL₂) and cobalt(II) (CoL₂), were synthesized and utilized as diesel additives for the first time. Experiments were conducted on a 1.5-L, four-cylinder engine at 1750 rpm under three load conditions: 50, 75, and 100 Nm. The results demonstrated that 25 ppm of NiL₂ and CoL₂ altered the combustion kinetics. At medium loads, the additives increased maximum cylinder pressure by 3% and shortened ignition delay at low loads. Peak heat release and heat transfer rates improved by 4% and 7%, respectively. CoL₂ exhibited the most pronounced thermal effect, raising average in-cylinder gas temperatures by up to 4% at high loads. However, despite these thermodynamic changes, the additives did not yield any reductions in NO, HC, or CO emissions; in fact, emission levels were generally similar to or slightly higher than those of neat diesel. These findings suggest that while these specific complexes act as combustion modifiers that enhance in-cylinder thermal parameters, they do not offer significant advantages regarding emissions under the tested configurations. Full article

Introduction: One of the fundamental principles of modern medicine, including dentistry, is prevention. However, if treatment is not initiated, tooth loss can occur, necessitating the use of dental prostheses to restore the function and aesthetics of the stomatognathic system. The oral microbiome is a complex ecosystem that is sensitive to external factors, including the biomaterials used to manufacture dental prostheses. Objectives: This narrative literature review aims to identify and compare the effects of various metal alloys used in dentistry, specifically high-precious (gold), precious (silver–palladium) and base (cobalt–chromium and nickel–chromium) alloys, as well as titanium, on the balance of the oral microbiome and biofilm formation. Results: The analysis indicates that gold, silver and palladium alloys demonstrate the most favourable biocompatibility and antibacterial properties, significantly reducing biofilm accumulation. Titanium and titanium-based alloys generally exhibit neutral properties under healthy conditions, although their biocorrosion products can alter the microbial environment in pathological states such as peri-implantitis. In contrast, base metal alloys (cobalt–chromium and nickel–chromium) are highly susceptible to biocorrosion in acidic environments, which can encourage the growth of bacteria that cause tooth decay and inflammation, potentially exacerbating oral dysbiosis. Conclusions: The selection of materials plays a critical role in maintaining oral microbial homeostasis and preventing plaque-related diseases. High-noble alloys and titanium are more biocompatible than base metal alloys. However, further long-term clinical trials and multi-species biofilm models are needed to fully understand these interactions between materials and microbes. Full article

The Murmansk Region (the Russian Arctic) faces severe environmental degradation due to heavy metal (HM) pollution from copper–nickel smelting, resulting in vast industrial barrens with elevated concentrations of copper (Cu) and nickel (Ni). Conventional phytostabilization methods are often ineffective or costly, necessitating alternative bioremediation strategies. This study evaluates the potential of microalgae and cyanobacteria for revegetating HM-contaminated substrates. Six strains of Nostoc-like morphotypes and three green microalgae were tested for Cu²⁺ tolerance (0.5–15 mg/L). While most strains exhibited growth inhibition at ≥3 mg/L Cu²⁺, Atlanticothrix sp. KPABG-154445, isolated from Tolbachik Volcano, showed positive growth at 2 mg/L Cu²⁺ under the tested conditions and recovering metabolic activity post-exposure. In sorption experiments, non-viable biomass achieved 68% Cu²⁺ removal at 2 mg/L, outperforming actively growing cultures. A microcosm experiment using copper-spiked nepheline slime (simulating mining waste) revealed Atlanticothrix sp. KPABG-154445’s ability to colonize nutrient-poor substrates, forming biocrusts covering 42% of the surface within one month, even under Cu²⁺ contamination (10 mg/kg). These findings highlight cyanobacteria, particularly strains such as KPABG-154445, as promising agents for the bioremediation of Arctic industrial barrens, leveraging their dual capacity for heavy metal tolerance and biocrust formation. Full article

This study investigated how acid concentration affects leaching from pyrolyzed LIBs’ (lithium-ion batteries’) black mass (BM) by stepwise acidification with eight acids at 70 °C under identical starting conditions. A citric-acid control without BM matched the calculated pH, whereas BM buffered solutions to ∼pH 9.5 and increased the measured pH. Stabilized pH provided a consistent reference within each experiment, but similar pH values across acids produced very different leaching efficiencies. At pH ≈ 3, lithium leaching was ∼pH 85% for formic acid and ∼pH 60% for citric acid. The maximum lithium leaching ranged from 49% (ascorbic acid) to 92% (sulfuric acid), while organic acids often showed limited cobalt and nickel dissolution. For formic acid, speciation and metal-formate solubility calculations showed that higher acid concentration does not necessarily increase transition-metal leaching and may suppress cobalt and nickel. Thus, pH is stable within each acid system but not transferable across acids, and high solid loading (250 g L⁻¹) further requires acid-specific evaluation. The results indicate that acid-dependent speciation and complexation, rather than proton concentration alone, control extraction and can decouple acid dosage from leaching performance. Full article

Sustainable coastal environmental management relies on continuous assessment of sediment quality. In the Saudi Arabian Red Sea, such sediments function as both sinks and potential secondary sources of heavy metals (HMs) originating from natural processes and anthropogenic activities. The present study investigated the concentrations of HMs in surface sediments from Jeddah and Rabigh. Contamination levels, as well as possible natural and anthropogenic inputs and potential risks to human health through ingestion, dermal contact, and inhalation pathways, were evaluated. The results indicated that Fe is the most abundant metal at both sites (1570.40 mg/kg at Jeddah and 1804.11 mg/kg at Rabigh). Cu, Ni, and Zn are present in the sediments at concentrations ranging between 3.12 and 4.49 mg/kg, while Cd and Pb remain below the detection limits in all samples. Generally, the contamination index values indicated low levels in both regions. The evaluation of human health risks identified ingestion as the primary exposure pathway. Non-carcinogenic risk levels were within safe limits for both adults and children. However, the carcinogenic risk assessment of nickel (Ni) indicated that all values fall within the acceptable range (10⁻⁶–10⁻⁴), although children consistently showed higher risks than adults. Despite the overall low levels of pollution, the moderate enrichment of Cu, Ni, and Zn in Jeddah and Cu in Rabigh, along with the higher non-carcinogenic risks to children at the Rabigh site, highlights the need for continuous environmental monitoring and further investigation to support the sustainable management of coastal ecosystems. Full article